1. Field of the Invention
The present invention relates to toys and toy systems which include photochromatic materials which change in appearance when subjected to ultraviolet (UV) light, and in particular to such toys and/or toy systems comprising movable cars, such as, for example, those included in model railways.
2. Background Art
Photochromatic materials are chemical compounds which exhibit a reversible change in its absorption spectrum upon irradiation with light of a given wavelength. Photochromatic compounds may be engineered to exhibit this change in the absorption spectrum at light wavelengths below those of visible light, the absorption spectrum change being manifested by a change in the color of the material. Thus, the material may exhibit one, "natural" color when exposed to visible light, and another, different color when exposed to light of a shorter wavelength.
Ultraviolet (UV) radiation is electromagnetic radiation in the part of the light spectrum between x-rays and visible light, and differs from visible light only in that the UV wavelengths are too short to be seen by the human eye. UV light has wavelengths which vary from between about 100 to 400 nm; the wavelength of visible light ranges from about 330 to 770 nm. UV light is generally characterized into three ranges: UVA (315 to 400 nm); UVB (280 to 315 nm); and UVC (200 to 280 nm). Light of wavelengths from 100 to 200 nm may also be considered to be a shorter range of UVC. UVB radiation, for example, is of the type used for suntanning, whereas UVC radiation may be used for germicidal disinfection; these types of light may be damaging to human cells. The well-known fluorescent or incandescent blacklight, however, emits UVA light radiation.
Many accessories which simulate activities related to rail transport are known and available for the model railroad hobbyist, and it is known to provide toy elements which represent various things which are transported by the model train. Such representative elements include, for example, people, animals, luggage, vehicles and other manufactured goods. Moreover, it is known to provide life-like miniature environments in which these elements are animated such that they may be moved about to simulate work being done by the people or on the goods.
Further, it is known to provide a model railroad accessory which comprises a representative element which simulates a container, such as a bottle. Previously, however, because the appearance of these representative elements have been substantially fixed, they have only simulated a single condition. For example, previous elements which represent bottles have been painted or molded in color, and thus may simulate only the containers' full or empty conditions. Separate, differently colored elements would be necessary to simulate the containers' empty condition.
A toy system, such as a model railway in combination with an accessory, in which a representative element may be altered in appearance to simulate a change in condition of thing it represents, without necessitating separate representative elements to simulate the separate conditions, is desirable. Further, it is desirable to provide a toy system in which a single representative element may be used to simulate both the presence and absence of something associated with the simulated element, which would, in the real world, be transported by rail. In particular, it is desirable to provide such a system in which the representative elements are separable from the train in which they are conveyed, and are animated during the time they are separated from the train.